The drilling's and vierling's are nice if you have a gunbearer! In Europe the 16 gauge was popular because it reduced the weight of these guns. The single shotgun and rifle combos were also popular for being lighter guns. They were called
bockbuchsflinte. All three types are still used in Europe.
I have two of the combo guns. A Sabbiti 12 gauge over 6.5X57R, double trigger with 26" barrels. It a beautiful gun with engraved side panels, its only draw back is the barrels are completely soldered and can not be regulated like the Valmet/Tikka/Marrochi's.
I like my Valmet 412 because I can zero my scope for the shotgun pattern at 40 yards and then regulate the rifle barrel to hit where the scope is aimed at 100 yards. It also has a lite crisp trigger. The barrels are 23.5", a bit on the short side, but very useable. My 12ga loads are Federal Gold Metal hulls, 2 3/4". Loaded to 1 1/4 oz. with 60 BBB lead shot at 1385 fps. These will place 8 to 14 pellets in a 10" paper plate at 40 yards. The .223 rem barrel shoots 55 gr bullets at sub MOA.
The Valmet 412's come up for sale occasionally in online auctions. Valmet also made this system for Savage years ago called Savage/Valmet, 330 and 2400. The 330's were o/u shotguns and the 2400's were combo guns. The barrels can be used on either receivers. There is a 2400, 12ga over 22HP,
https://www.gunbroker.com/item/804127171 currently on gunbroker for $700.00. And A Valmet 412, 12 ga over 22HP,
https://www.gunbroker.com/item/816108123, for $900.00. Which are good prices for a combo varmint gun. The combo barrels come in many different calibers. More common calibers bring higher prices.